The present invention is directed to a propulsion system for a marine vessel comprising a steerable propeller including an under water housing enclosing drive gears and connected to a ship's propeller. The housing is fixed to the lower end of a steering tube which is coupled to a swivel drive at its upper end, the driving shaft for the propeller being accommodated therein. The steerable propeller further includes a sleeve for enclosing the under water housing, propeller, steering tube, swivel-drive and driving shaft, means for guiding the propeller and under water housing within the sleeve, for lowering the assembly below said sleeve and for subsequently raising same, the steerable propeller being provided with a motor near the upper part of the sleeve, the shaft of said motor being coupled with the driving shaft of the propeller.
Similar, steerable propellers are known in different variants and are mounted in a vessel or other floating craft, either for steering them or for retaining them at a defined position (so called dynamic positioning). In certain circumstances, such as when the vessel is sailed in shallow areas or when entering a port, the under water housing with the propeller is raised within the sleeve, thereby preventing the protrusion of vulnerable parts from the bottom of said sleeve. This raising of the under water housing and its successive lowering is a drastic undertaking, whereby not only very large masses have to be displaced, but whereby also parts of the steerable propeller may protrude above the deck of the vessel, particularly the driving shaft and the motor coupled therewith (driving set), which participate in the vertical movement of the assembly.